The carbon in the media w ill diffuse in microstructure, which not only embrittles the tubes, but also pro duces the residual stresses on their surface.For these reasons, the tubes crack .

• 当炉管长期在高温下工作时，介质中的碳会渗入到显微组织中，这不仅使材料脆化，而且使渗碳表面产生残余应力，导致炉管开裂。